1. Field of the Invention
The present invention relates to a secondary battery such as a non-aqueous electrolyte secondary battery or the like.
2. Description of the Related Art
In recent years, a secondary battery such as a non-aqueous electrolyte secondary battery or the like attracts attention as a power source of a hybrid electric vehicle or electric storage device for an electric generator that uses natural energy such as sunlight or wind. In general, a non-aqueous electrolyte secondary battery is provided with an exterior member constituted of a metallic container, a laminate film or the like, an electrode body contained in the exterior member together with an electrolyte liquid, and electrode terminals connected to the electrode body, and exposed to the outside.
The electrode body is configured by laying a negative electrode obtained by forming a negative electrode active material layer on a current collector plate on top of a positive electrode obtained by forming a positive electrode active material layer on a current collecting plate with a separator interposed between the electrodes, and rolling up the electrodes and separator into a spiral shape. Further, tabs for current collection are extended from a side edge of the current collector plate.
For example, in Jpn. Pat. Appln. KOKAI Publication No. 2006-79942, a non-aqueous electrolyte secondary battery provided with a rolled-up electrode body, in which the start and end of the roll are tapered to prevent short circuiting the electrodes due to rolling displacement occurring at the time of rolling up the negative electrode and positive electrode is proposed.
According to the non-aqueous electrolyte secondary battery configured as described above, it becomes possible to secure a sufficient charge and discharge capacity, and prevent the battery performance from lowering. However, in the conventional non-aqueous electrolyte secondary battery, when the temperature inside the battery rises for some reason, thermal contraction occurs in the separator for electrically insulating the positive electrode and negative electrode from each other, whereby the positive and negative electrodes are short-circuited, and the short-circuit current causes further heat generation, leading to thermal runaway, in some cases. For example, it is known that the internal temperature of a battery rises when overcharging above the rated charge is carried out inadvertently, and depending on the circumstances, there is the possibility of thermal runaway being caused due to thermal contraction of the separator.